DESCRIPTION (Abstract of the project) Project 1 ("Mechanism of Tubulointerstitial Disease in Obstructive Nephropathy") will test the hypothesis that activation by angiotensin II of tumor necrosis factor-a (TNF-a) and members of the nuclear factor Kappa B (NF-kB) family mediates the inflammation and fibrosis of the tubulointerstitium of the kidney in a model of obstructive nephropathy. This proposal has several postulates: 1.) angiotensin II-mediates NF-kB activation during the initial stages of renal disease and upregulates TNF-a mediating events contributing to fibrosis of the kidney: 2) TNF-a mediates, in turn, NF-kB activation and sustains the maintenance of renal fibrosis and 3) maneuvers that blunt the increase in classical NF-kB transactivators should ameliorate or reverse the cellular events leading to fibrosis of the kidney in vivo. The specific aims of this project include: 1) to determine the molecular cellular events mediated by AT1, AT2, TNFR1 or TNFR2 receptors leading to activation of NF-kB during the development and maintenance of renal fibrosis in vivo, 2) to determine the mechanisms by which angiotensin activates NF-kB and increases TNF-a production in vitro, 3) determine the mechanism by which TNF-a activates NF-kB and, increases its own induction in vitro and 4) to determine the effects of inhibiting NF-kB activation in vivo on the reversibility of renal fibrosis and the recovery of renal function. We will utilize mice with specific mutations that functionally inactivate the individual angiotensin II receptors or the TNF-a receptors. In these mice unilateral ureteral ligation will be performed and the histology of the obstructed kidney in the knockout mice will be compared to that of the wild type. Release of obstruction at different intervals after ureteral ligation will be performed and tissue analyzed for changes in histological features. Cultures of kidney cells from wild type and mice with receptor mutations, will be utilized to examine the molecular events by which angiotensin II activates NF-kB and TNF-a.